1. Field of the Invention
The present invention relates to an organic light-emitting diode with high efficiency and a long lifetime. More particularly, the present invention relates to an organic light-emitting diode that can emit deep blue light as well as having high efficiency and a long lifetime.
2. Description of the Related Art
Organic light emitting diodes (OLEDs), based on self-luminescence, are used to create digital displays with the advantage of being able to be thinner and lighter than liquid crystal displays (LCDs). In addition, an OLED display exhibits a much faster response time than an LCD. Accordingly, organic light emitting diodes find applications in the illumination field as well as the full-color display field.
Materials used as the organic layers in organic light emitting diodes may be divided into luminescent materials and charge carrier materials, for example, a hole injection material, a hole transport material, an electron injection material, and an electron transport material. According to the luminescent materials, there are two main families of OLED: those based on small molecules and those employing polymers. The light emitting mechanisms allows the luminescent materials to be classified as fluorescent and phosphorescent materials, which use excitons in singlet and triplet states, respectively.
Meanwhile, when a single material is employed as the luminescent material, intermolecular actions cause the maximum luminescence wavelength to shift toward a longer wavelength, resulting in a reduction in color purity and light emitting efficiency. In this regard, a host-dopant system may be used as a luminescent material so as to increase the color purity and the light emitting efficiency through energy transfer.
This is based on the principle that, when a dopant is smaller in energy band gap than a host accounting for the emissive layer, the addition of a small amount of the dopant to the host generates excitons from the emissive layer so that the excitons are transported to the dopant, emitting light at high efficiency. Here, light of desired wavelengths can be obtained depending on the kind of the dopant because the wavelength of the host moves to a wavelength range of the dopant.
With regard to related arts of dopant compounds in the emissive layer, reference may be made to Korean Patent Unexamined Application Publication No. 10-2008-0015865 (Feb. 20, 2008), which describes an organic light emitting device using an arylamine-coupled indenofluorene derivative, and Korean Patent Unexamined Application Publication No. 10-2012-0047706 (May 14, 2012), which describes an organic photoelectric device using a compound in which dibenzofuran or dibenzothiophene coexists with fluorene or carbazole.
In recent years, studies have been conducted on organic light emitting compounds having high efficiency and a long lifetime, and are ongoing particularly on organic light-emitting diodes using blue light-emitting compounds having high efficiency and a long lifetime.
As a related art for an organic light-emitting diode using a blue light-emitting compound, mention may be made of Korean Patent Unexamined Application Publication No. 10-2011-0015213 (Jan. 15, 2011) in which pyrene arylamine derivatives with various substituents on the aryl moiety are used for organic light-emitting diodes.
Given a CIE of 0.1 or less for deep blue, however, most of the pyrene derivatives are poor in efficiency and have a short lifetime. Despite various efforts made to solve the problems, there is still continuation of a need for the development of a novel organic light-emitting diode that exhibits higher efficiency and a longer lifetime than conventional organic light-emitting diodes.